A cellular radio access network is a collection of cells that each includes at least one base station capable of transmitting and relaying signals to subscribers' mobile nodes. A “cell” generally denotes a distinct area of a mobile network that utilizes a particular frequency or range of frequencies for transmission of data. A typical base station is a tower to which are affixed a number of antennas that transmit and receive the data over the particular frequency. Mobile nodes, such as cellular or mobile phones, smart phones, camera phones, personal digital assistants (PDAs) and laptop computers, may initiate or otherwise transmit a signal at the designated frequency to the base station to initiate a call or data session and begin transmitting data.
Mobile service provider networks convert cellular signals, e.g., Time Division Multiple Access (TDMA) signals, Orthogonal Frequency-Division Multiplexing (OFDM) signals or Code Division Multiple Access (CDMA) signals, received at a base station from mobile nodes into Internet protocol (IP) packets for transmission within packet-based networks. A number of standards have been proposed to facilitate this conversion and transmission of cellular signals to IP packets, such as a general packet radio service (GPRS) standardized by the Global System for Mobile Communications (GSM) Association, a Universal Mobile Telecommunications System (UMTS), an evolution of UMTS referred to as Long Term Evolution (LTE), as well as other standards proposed by the 3rd Generation Partnership Project (3GPP), 3rd Generation Partnership Project 2 (3GGP/2) and the Worldwide Interoperability for Microwave Access (WiMAX) forum.
A typical mobile service provider network, or mobile network, includes a core packet-switched network, a transport network, and one or more radio access networks (RANs). The core packet-switched network for the mobile network establishes logical connections, known as bearers, among the many service nodes on a path between a mobile node, attached to one of the radio access networks, and a packet data network (PDN). The service nodes then utilize the bearers to transport subscriber traffic exchanged between the mobile node and the PDN, which may include, for example, the Internet, an enterprise intranet, a layer 3 VPN, and a service provider's private network. Various PDNs provide a variety of packet-based data services to mobile nodes to enable the mobile nodes to exchange service data with application or other servers of the PDNs.
Some mobile nodes, in addition to supporting connections to a mobile network via a RAN, also support wireless local area network (WLAN) access network connections that provide connectivity to a broadband network via a WiFi “hotspot” or other wireless access point (WAP). These mobile nodes may support WLAN offload while dual-connected to a RAN of a mobile service provider network as well as to a WLAN access network that is not connected to the mobile service provider core packet-switched network. That is, such mobile nodes may route specific IP flows via the WLAN access network rather than via the RAN in order to avoid traversing the mobile service provider network. However, in such cases, a mobile node uses the local IP address allocated by the WLAN for such IP flows, and neither the WLAN nor mobile service provider network provides IP address preservation to the mobile node to allow “seamless” WLAN offload for IP flows to permit uninterrupted operation of higher-level protocols. While overlay networks that tunnel IP flows between a WLAN and a mobile service provider network or between multiple mobile service provider networks may provide inter-network connectivity, such overlay networks prevent the service providers from enforcing traffic policies. In addition, overlay networks require that the roaming mobile node participate in establishing a tunnel to connect itself to an anchor point of the mobile service provider network for the mobile node.